Expression of a fungal ferulic acid esterase increases cell wall digestibility of tall fescue (Festuca arundinacea)
Expression of a fungal ferulic acid esterase increases cell wall digestibility of tall fescue (Festuca arundinacea)
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DOI：
10.1111/j.1467-7652.2007.00317.x
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发表时间：
2008-04-01
影响因子：
13.8
通讯作者：
Morris, Phillip
中科院分区：
文献类型：
--
作者：
Buanafina, Marcia M. de O.;Langdon, Tim;Morris, Phillip
在牧草细胞壁中，阿魏酸被酯化成阿拉伯木聚糖，并与木质素单体参与氧化偶联途径，生成阿魏酸-多糖-木质素复合物，交联细胞壁。这种交联阻碍了反刍动物微生物对细胞壁的降解，降低了植物的消化率。在本研究中，制备了表达针对液泡的黑曲霉阿魏酸酯酶（FAEA）的转基因羊茅属植物。水稻肌动蛋白启动子对FAEA表达有效，花椰菜花叶病毒（CaMV） 35S和玉米泛素启动子也是如此。然而，在诱导热休克和衰老启动子中发现了更高水平的表达。在细胞死亡和随后的孵育后，液泡靶向FAEA导致细胞壁释放单体和二聚体阿魏酸，并且通过添加外源性内切-1,4- β -木聚糖酶可将其增强数倍。与未转化的植物相比，大多数表达faea的植物显示出更高的消化率和更低的细胞壁酯化酚水平。综上所述，FAEA的靶向表达是提高羊茅和其他用于饲料或纤维素乙醇生产的禾本科植物壁消化率的有效策略。
In the cell walls of forage grasses, ferulic acid is esterified to arabinoxylans and participates with lignin monomers in oxidative coupling pathways to generate ferulate-polysaccharide-lignin complexes that cross-link the cell wall. Such cross-links hinder cell wall degradation by ruminant microbes, reducing plant digestibility. In this study, genetically modified Festuca arundinacea plants were produced expressing an Aspergillus niger ferulic acid esterase (FAEA) targeted to the vacuole. The rice actin promoter proved to be effective for FAEA expression, as did the cauliflower mosaic virus (CaMV) 35S and maize ubiquitin promoters. Higher levels of expression were, however, found with inducible heat-shock and senescence promoters. Following cell death and subsequent incubation, vacuole-targeted FAEA resulted in the release of both monomeric and dimeric ferulic acids from the cell walls, and this was enhanced several fold by the addition of exogenous endo-1,4-beta-xylanase. Most of the FAEA-expressing plants showed increased digestibility and reduced levels of cell wall esterified phenolics relative to non-transformed plants. It is concluded that targeted FAEA expression is an effective strategy for improving wall digestibility in Festuca and, potentially, other grass species used for fodder or cellulosic ethanol production.